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Increased phosphorylation of myosin light chain associated with slow-to-fast transition in rat soleus.
Am J Physiol Cell Physiol. 2003 Sep; 285(3):C575-83.AJ

Abstract

In striated muscles myosin light chain (MLC)2 phosphorylation regulates calcium sensitivity and mediates sarcomere organization. Little is known about the changes in MLC2 phosphorylation in relation to skeletal muscle plasticity. We studied changes in MLC2 phosphorylation in rats receiving three treatment conditions causing slow-to-fast transitions: 1) atrophy induced by 14 days of hindlimb suspension (HS), 2) hypertrophy induced by 14 days of clenbuterol administration (CB), and 3) 14 days of combined treatment (CB-HS). Three variants of the slow (MLC2s) and two variants of the fast MLC2 (MLC2f) isoform were separated with two-dimensional electrophoresis and identified with monoclonal and polyclonal antibodies specific for MLC2; their relative proportions were densitometrically quantified. In control soleus muscle MLC2s predominated over MLC2f (91.4 +/- 3.9% vs. 8.5 +/- 3.9%) and was separated into two spots, the less acidic spot being 73.5 +/- 4.3% of the total. All treatments caused a decrease of the less acidic unphosphorylated spot of MLC2s (CB: 64.1 +/- 5.6%, HS: 62.4 +/- 6.8%, CB-HS: 56.4 +/- 4.4%), the appearance of a third more acidic variant of MLC2s (representing 3.9-5.9% of total MLC2s), an increase of MLC2f (CB: 30.9 +/- 3.1%, HS: 23.9 +/- 3.3%, CB-HS: 25.3 +/- 3.9%), and the phosphorylation of a large fraction of MLC2f (CB: 30.4 +/- 6.7%, HS: 28.7 +/- 6.5%, CB-HS: 21.8 +/- 2.1%). Treatment with alkaline phosphatase or with protein phosphatase 1 (PP1) removed the most acidic spots of both MLC2f and MLC2s. We conclude that in rat skeletal muscles an increase of MLC2 phosphorylation is associated with the slow-to-fast transition regardless of whether hypertrophy or atrophy develops.

Authors+Show Affiliations

Department of Anatomy and Physiology, University of Padova, Via Marzolo 3, 35131 Padua, Italy.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12748068

Citation

Bozzo, Cyril, et al. "Increased Phosphorylation of Myosin Light Chain Associated With Slow-to-fast Transition in Rat Soleus." American Journal of Physiology. Cell Physiology, vol. 285, no. 3, 2003, pp. C575-83.
Bozzo C, Stevens L, Toniolo L, et al. Increased phosphorylation of myosin light chain associated with slow-to-fast transition in rat soleus. Am J Physiol Cell Physiol. 2003;285(3):C575-83.
Bozzo, C., Stevens, L., Toniolo, L., Mounier, Y., & Reggiani, C. (2003). Increased phosphorylation of myosin light chain associated with slow-to-fast transition in rat soleus. American Journal of Physiology. Cell Physiology, 285(3), C575-83.
Bozzo C, et al. Increased Phosphorylation of Myosin Light Chain Associated With Slow-to-fast Transition in Rat Soleus. Am J Physiol Cell Physiol. 2003;285(3):C575-83. PubMed PMID: 12748068.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Increased phosphorylation of myosin light chain associated with slow-to-fast transition in rat soleus. AU - Bozzo,Cyril, AU - Stevens,Laurence, AU - Toniolo,Luana, AU - Mounier,Yvonne, AU - Reggiani,Carlo, Y1 - 2003/05/14/ PY - 2003/5/16/pubmed PY - 2003/9/26/medline PY - 2003/5/16/entrez SP - C575 EP - 83 JF - American journal of physiology. Cell physiology JO - Am J Physiol Cell Physiol VL - 285 IS - 3 N2 - In striated muscles myosin light chain (MLC)2 phosphorylation regulates calcium sensitivity and mediates sarcomere organization. Little is known about the changes in MLC2 phosphorylation in relation to skeletal muscle plasticity. We studied changes in MLC2 phosphorylation in rats receiving three treatment conditions causing slow-to-fast transitions: 1) atrophy induced by 14 days of hindlimb suspension (HS), 2) hypertrophy induced by 14 days of clenbuterol administration (CB), and 3) 14 days of combined treatment (CB-HS). Three variants of the slow (MLC2s) and two variants of the fast MLC2 (MLC2f) isoform were separated with two-dimensional electrophoresis and identified with monoclonal and polyclonal antibodies specific for MLC2; their relative proportions were densitometrically quantified. In control soleus muscle MLC2s predominated over MLC2f (91.4 +/- 3.9% vs. 8.5 +/- 3.9%) and was separated into two spots, the less acidic spot being 73.5 +/- 4.3% of the total. All treatments caused a decrease of the less acidic unphosphorylated spot of MLC2s (CB: 64.1 +/- 5.6%, HS: 62.4 +/- 6.8%, CB-HS: 56.4 +/- 4.4%), the appearance of a third more acidic variant of MLC2s (representing 3.9-5.9% of total MLC2s), an increase of MLC2f (CB: 30.9 +/- 3.1%, HS: 23.9 +/- 3.3%, CB-HS: 25.3 +/- 3.9%), and the phosphorylation of a large fraction of MLC2f (CB: 30.4 +/- 6.7%, HS: 28.7 +/- 6.5%, CB-HS: 21.8 +/- 2.1%). Treatment with alkaline phosphatase or with protein phosphatase 1 (PP1) removed the most acidic spots of both MLC2f and MLC2s. We conclude that in rat skeletal muscles an increase of MLC2 phosphorylation is associated with the slow-to-fast transition regardless of whether hypertrophy or atrophy develops. SN - 0363-6143 UR - https://www.unboundmedicine.com/medline/citation/12748068/Increased_phosphorylation_of_myosin_light_chain_associated_with_slow_to_fast_transition_in_rat_soleus_ L2 - https://journals.physiology.org/doi/10.1152/ajpcell.00441.2002?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -